One-hundred years ago last week, May 7th 1915, a German U-Boat fired a torpedo into the passenger ship RMS Lusitania off the coast of Ireland killing 1200 of the 2000 people on board. It’s the other Titanic.

Punch cartoon on the sinking of the Lusitania, 1915. Photo: AFP

Author Erik Larson, known as the master of narrative, historic non-fiction said the Lusitania was special.

“With World War I underway, it was the biggest most glamorous ocean liner in service” he says. “You could book a state room that had a wood burning fire place”.

Larson says other mighty ocean liners of the era were either commandeered into military service or parked in neutral harbors for safe keeping. Not the Lusitania.

“It was considered so big and so fast people assumed or believed no submarine could catch it” Larson says.

His new book 'Dead Wake: The Last Crossing of the Lusitania' tells the story of the doomed ship, the German submarine that hunted her, the dramatic 18-minute sinking, and the 100-year-old controversy about information on the German U-boats lurking in the area that was never passed on to the Lusitania.

Dead Wake - The Last Crossing of the Lusitania by Erik Larsen. Photo: Supplied

On the morning of May 1st, 1915, as passengers were preparing to leave New York city bound for Liverpool, the German Embassy placed an ad in the newspapers “warning anyone sailing across the Atlantic that they did so at their own risk because it was a war zone. In the New York World paper, the notice appeared right next to an advertisement for Cunard. The ad was widely interpreted as a direct warning about the Lusitania, according to Larson.

But the passengers took no notice. They believed a passenger ship would be off limits to German U-Boat attack. Larson says evidence shows that passengers believed they would have protection in the North Altantic.

“It seems clear from passenger accounts that Cunard was telling passengers before the voyage began that they would be under the watchful guard of the Royal Navy as the ship entered the so called war zone."

No Royal Navy escorts were dispatched as the Lusitania approached the Irish Coast on a beautiful spring afternoon on May 7th, 1915.

“The sea was absolutely flat and glassy. At this point, about 2 o’clock, the passengers were congratulating themselves that they had at last made it. They had not been torpedoed, all is good and they’re going to arrive in port the next day” Larson describes.

Many passengers were on deck looking out at the sea when they saw it.

“Suddenly there is a track of a torpedo. It was such an almost miraculous event everyone had feared and dreaded and now here it is. Here’s this thing coming across the glassy sea. They could see the compressed air wake on the surface”.

One torpedo fired by German Captain Walther Schwieger was all it took.

“There is this confluence of chance events that led to the fact that this gigantic ship would sink in 18 minutes because of a single torpedo. No ship engineer would have forecast that was possible” Larson says. But it hit in just the right place causing catastrophic flooding. The Lusitania began to list at 25 degrees.

Because of the Titanic disaster just a few years before, there were plenty of lifeboats on the Lusitania for everyone.

“The problem is when you have a ship leaning at 25 degrees half the lifeboats were useless. How do you get across 8 feet of open space 60 feet above the ocean surface into the lifeboat? “ asks Larson.

Only 6 lifeboats were successfully launched. Most of the survivors simply jumped overboard with their life vests. Larson writes about one passenger, Dwight Harris, who brought his own custom made life belt. In a letter to his Mother, Larson says he detailed the last minutes of the Lusitania.

“He watched this giant ship go by. He could see the whole panorama of death and despair and smoke and everything as the ship past and sank” says Larson.

Postcard of the cruise liner Lusitania, 1912. Photo: AFP

Conspiracy theories about the sinking of the Lusitania have swirled around for 100 years. Questions remain about what British Naval intelligence knew, and why the information was never shared with the Captain of the Lusitania. In the book, Larson describes an ultra secret agency called Room 40 which had been decoding German U-boat messages since the start of the war.

“Room 40 knew exactly where it was headed which was a patrol zone just off the coast of Liverpool and that was where the Lusitania was going” Larson reveals. The Captain was never told. They also knew the U20 had torpedoed 3 much smaller vessels in the vicinity.

So a question remains: why wasn’t the Lusitania warned about the U-Boat. There is speculation that Winston Churchill or someone in the Admiralty was involved.

“Whoever engineered this wanted the Lusitiania to be attacked as a way of getting America to join the war” says Larson. “Whether that had anything to do with why the Lusitania was left unprotected and was given so little information, I will leave that to the conspiracy theorists”.